Got offered a pretty good deal on the m920, so decided to roll the dice.
Now have the Grace m920 in house to compare to my m903.
While I've only just got the m920, I'll offer some preliminary impressions.
Externally these two DAC/preamps are virtual twins (back panel identical) and operation is the same as well.
I peeked under the hood of the m920 and here its obvious that the pcb has had an extensive redesign to accommodate the 9018 2M dac chip.
Speaking of the dac - that thing is freaking tiny!! - around the same size a surface mount dual opamp!
While much has changed on the pcb, there is also a lot of carry over.
The headphone amp uses the same device and appears identical. The analog input receivers, dac I/V, filter and SE output chips are the same. A good thing IMO as Grace Design seems to have put a bit of thought into the components chosen for these tasks. Many other designs just choose an opamp part and use it everywhere regardless of function.
I inserted the m920 directly in place of the m903 which I was using as a dac/preamp in my system.
I haven't done any swapping in/out (yet) - but I'm pretty familiar with the 903, having owned it for 2 years.
System chain: Mac Mini > iFi usb power filter/Gemini usb cable > usb input m920 , SE output > Odyssey Khartago power amp > Harbeth Monitor 30.1 speakers.
Headphones are the notoriously inefficient HiFiman HE-6. Some may raise their eyebrows at the HE-6, but I used them with the m903 and it proved perfectly adequate for the task and sounded very good.
Just a word on the remote. I recently bought a Grace remote for my m903 as I had some issues using (some of) the 902 codes on the Harmony database(no 903 codes).
I was surprised to find that this functions perfectly for the m920. I went back and checked the box it came in - and found that it was actually labelled as an m920 remote.
For some reason I was under the impression the codes had been changed from the m903 - but I can verify they're the same. Furthermore the Harmony codes for the m920 work fine -
so I imagine these will also work perfectly for the m903 as well (haven't actually tried this yet) -
tried, didn't work, see below.
So after a decent warm-up I had a listen. Initially I wasn't overwhelmed/blown away by any drastic change, but as I listened I became convinced that the m920 is an emphatic leap forward.
For starters, it's hard to miss the increase in clarity - not just of individual performers, but also resolution of the soundspace. This gives more 'thereness' to everything - you feel closer to recording because there is more 'realness' to familiar sounds. Instruments/performers are more easily untangled and separated from the mix with more space around them. Individual sounds/voices are more easily recognised - ie the individual characteristics of different voices etc become clearer. On a similar line, the differences between recordings - or even tracks - is more emphatic. This is always a good sign IMO as it speaks highly of the transparency of the device.
BTW you don't have to use hi-res recordings to hear these changes (though I did) - the improvements are clearly audible even on MP3 quality material (Spotify premium).
In regard to hi-res recordings, my initial impression is that the benefits of these are more obvious through the m920 than the m903 - no doubt due to the increase in clarity and resolution.
While most of my listening so far has been through my Harbeth monitors, I've done some with the HE-6. I can confirm the m920 is just as adept at driving the HE-6 as the m903 (as expected) but that the increased clarity is very apparent. This not only gives more precise imaging but also a more spacious out of the head sound to the HE-6's. Bass sounds awesome through the HE-6's - more powerful/solid/defined than the m903 - which is kind of weird since the headphone amp is identical and this must be down to the dac and other minor tweaking. The best thing is that the more precise/resolved sound is not at the expense of any added brightness. There is greater clarity and openness to HF instruments, but they don't sound brighter. I was worried about this as the HE-6 has a reputation of exposing brightness due to its balance. In fact, if anything, I think the m920 has a more refined sound. These benefits are easy to hear with the HE-6's.
I'll probably have more to say after more listening, but suffice to say I'm very pleased with my purchase. While value judgements may vary from person to person, I believe the upgrade from the m903 to m920 is very worthwhile - particularly if you're as sold on the features/functionality of the m903 as I was.
EDIT: I tried the 920 codes, from the online Harmony database, on the m903 - they DIDN'T work! Which is really weird because the Grace remote works perfectly with either m903 or m920. If I use the Grace remote to program my Harmony it works fine with the m903.